Process for continuous continuous casting of hot liquid metals

ABSTRACT

The disclosure relates to a process for continuous continuous casting in which melts of different chemical compositions are successively cast into a water-cooled mould to form a continuous bar. When casting a melt of one composition is terminated, a metallic body is inserted into the mould so that it may weld with said melt, and then casting is continued with a melt of another composition which, in turn, welds with said metallic body. By this process the formation of transitional zones comprising a mixture of melts of different chemical compositions is avoided.

United States Patent [191 Bachner Feb. 5, 1974 PROCESS FOR CONTINUOUS CONTINUOUS CASTING OF HOT LIQUID METALS Inventor: Ernst Bachner, Linz, Austria Assignee: Vereinigte Osterreichische Eisen-und Stahlwerke Aktiengesellschaft, Linz, Austria Filed: Nov. 30, 1971 Appl. No.: 203,162

Foreign Application Priority Data Dec. 2, 1970 Austria A 10 838 US. Cl 164/82, 164/95, 164/244 Int. Cl B22d 23/00 Field of Search l64/274, 95, 82

References Cited UNITED STATES PATENTS 3/1963 Pearson et al. 164/274 FOREIGN PATENTS OR APPLICATIONS 4,113,722 8/1966 Japan 164/274 Primary Examiner-J. Spencer Overholser Assistant ExaminerJohn E. Roethel Attorney, Agent, or FirmBrumbaugh, Graves, Donohue & Raymond [57] ABSTRACT The disclosure relates to a process for continuous continuous casting in which melts of different chemical compositions are successively cast into a water-cooled mould to form a continuous bar. When casting a melt of one composition is terminated, a metallic body is inserted into the mould so that it may weld with said melt, and then casting is continued with a melt of another composition which, in turn, welds with said metallic body. By this process the formation of transitional zones comprising a mixture of melts of different chemical compositions is avoided.

2 Claims, 1 Drawing Figure PROCESS FOR CONTINUOUS CONTINUOUS CASTING OF HOT LIQUID METALS The invention relates to a process for continuous continuous casting of hot liquid metals, in which melts of different chemical compositions are successively cast into a water-cooled mould to form a continuous bar which is drawn out of the mould and further cooled.

Processes for continuous continuous casting are already known. To this end, when a casting ladle is empty, it has to be exchanged for a full ladle as quickly as possible; the amount of liquid metal present in the tundish of the continuous casting plant has to be sufficient so that the time necessary for exchanging the ladles can be bridged. Further, provisions have to be made for enabling the exchange of a tundish with worn refractory lining for a tundish which is ready for operation in a stand-by position without interrupting the casting process. A plant for continuous continuous casting which meets this requirement is, for example, described in the British Pat. specification No. 1 212 918, US Pat. No. 3 552 902. It has been possible to cast in such a plant a plurality of melts successively to form a continuous bar, using melts of the same or very similar chemical compositions. However, it has not been possible to cast melts with different chemical compositions to form a continuous bar, because on transition from a melt with the one composition to a melt with another composition, a bar portion comprising a mixture of both melts is formed, the longitudinal extension of which differs according to the casting and solidification conditions. This transition part has to be eliminated from the bar and falls either to the scrap or may be used for purposes with the least quality requirements; the yield of satisfactory continuous castings is thus reduced.

The invention is aimed at avoiding these disadvantages, i.e., at furnishing the prerequisites enabling melts of different composition to be cast to a continuous bar without loss; in a process of the kind defined in the introduction the invention resides in that on termination of casting a melt with the one composition (A), a metallic body, preferably a plate adapted to the cross section of the mould, is inserted into the mould and welds with the melt of the composition (A), whereupon casting is continued with a melt of another composition (B) which, in its turn, welds with the metallic body.

A device for carrying out the process according to the invention is characterized by a metallic body, preferably a plate, having hook or rail-shaped projections on both faces whcih body may be inserted into the hollow space of a continuous casting mould and temporarily supported by means of meltable brackets on the upper margin of the mould.

ln order that the invention may be more fully understood, details of the invention shall now be described with reference to the accompanying drawing which is a vertical sectional view of a continuously cast bar and of a water-cooled mould.

Numeral l deontes a water-cooled continuous casting mould from which the continuous cast bar 2 is drawn out; said bar is further cooled in a secondary cooling means, not shown, and finally it is severed into several pieces by a separation means, likewise not shown. The cast bar 2 has a solidified bar shell 3 and a liquid core 4. The casting level, i.e., the surface of the hot liquid metal in the mould, is denoted with 5. During continuous casting the casting level 5 is covered with a casting powder which protects the steel against oxidation by air. If it is desired to change from a melt with a particular chemical composition A, for example a steel with a low carbon content, to a melt with another chemical composition B, for example alloyed steel with a high carbon content, the casting powder floating on the casting level 5 is removed when the casting of melt A is terminated, and a steel plate 6 having a thickness of about 15 to 50 mm is inserted into the hollow space of the mould. The cross section of the steel plate is adjusted to the cross section of the mould 1 but somewhat smaller than the latter so that an annular gap 7 of several millimeters width is present between the mould wall and the steel plate. The steel plate 6 may immerse into the liquid core 4 and welds with the liquid core on the whole surface so that a solid connection with the cast bar 2 is established. To facilitate this, the plate 6 may be brought to lie on the bar shell 3 and, additionally, be fixed for a short period in this position. The holding brackets 8 arranged on the plate 6 serve this purpose; they melt off when casting when melt B is continued. This melt B welds also with the steel plate 6; it is not possible that the melts mix. The thickness and the formation of the steel plate 6 as well as its chemical composition depend on the casting conditions, the

mould cross section and the casting materials; preferalby a material is used for the plate which has the same composition as one of the melts. Rail pieces 9 may be fixed to both faces of the steel plate 6 or the plate may be provided with similar, e. g., hook-shaped projections, so that both melts weld well with the steel plate 6. When the cast bar 2 is severed, the separating cut is suitably carried out in the plane defined by the steel plate 6 so that nothing of the bar material proper is lost; the cut width, as a rule, amounts to about 15 mm, i.e., it corresponds to about the thickness of the steel plate.

What is claimed is:

1. A process for continuously casting successive casting melts of different compositions wherein each melt is cast through a water cooled mould to form a continuous cast bar, the bar is drawn out of the mould and cooled, and a continuous strand of intimately connected sections is produced, comprising the steps of casting a melt of a first composition through the mould to form a continuous cast bar,

terminating the casting of the melt of the first composition,

inserting a metallic body into the mould, the metallic body having substantially the same size and shape as the cross section of the mould,

temporarily supporting the metallic body in the mould by meltable brackets,

welding the metallic body to the upstream end of the cast bar of the first composition,

casting a melt of a second composition into the mould to form a continuous cast bar, and

welding the metallic body to the downstream end of the cast bar of the second composition.

2. The process set forth in claim 1 wherein the metallic body is a plate having a thickness of 15 to 50 mm. 

1. A process for continuously casting successive casting melts of different compositions wherein each melt is cast through a water cooled mould to form a continuous cast bar, the bar is drawn out of the mould and cooled, and a continuous strand of intimately connected sections is produced, comprising the steps of casting a melt of a first composition through the mould to form a continuous cast bar, terminating the casting of the melt of the first composition, inserting a metallic body into the mould, the metallic body having substantially the same size and shape as the cross section of the mould, temporarily supporting the metallic body in the mould by meltable brackets, welding the metallic body to the upstream end of the cast bar of the first composition, casting a melt of a second composition into the mould to form a continuous cast bar, and welding the metallic body to the downstream end of the cast bar of the second composition.
 2. The process set forth in claim 1 wherein the metallic body is a plate having a thickness of 15 to 50 mm. 